The 2012 elections reached new heights in terms of the resources invested by outside groups, though some of the most expensive races of the cycle saw relatively small third-party expenditures.

But resources invested by outside groups greatly affected the overall cost of individual Congressional contests, even as that money proved not to be the determining factor in the outcome of every race. In California’s 52nd District, one of the costliest House races in the country, the outside spending slightly surpassed candidate spending, doubling the total cost of that campaign.

There are several ways to tabulate the cost of each race.

For this list, CQ Roll Call used the outside group spending figures for each race tracked by the Center for Responsive Politics and added the total disbursements (as of Nov. 26) filed to the Federal Election Commission by only the Democratic and Republican general election candidates. (One race featured two Democrats, thanks to California’s new primary format.) Outside group expenditures include funds invested by the congressional campaign committees, super PACs and political activist groups.

The following are the Top 5 most expensive House and Senate races, according to CQ Roll Call’s formula.

Senate Massachusetts: Republican Sen. Scott P. Brown vs. Democrat Elizabeth Warren

Candidates: $78,572,515

Outside: $6,856,819

Total: $85,429,334

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